[mythtv-users] Video studder XvMC w/OSD

[Roger Heflin]

W.Kenworthy wrote:
> On Wed, 2008-04-02 at 22:11 -0500, Roger Heflin wrote: 
>> W.Kenworthy wrote:
>>>> If it were, cpufreq would be speeding things up, and that is a fairly old cpu, 
>>>> and it pre-dates Intel putting speedstep on their desktop cpus, they only did 
> 
> ...
> 
>> Interesting.
>>
>> Fedora 8 has that module, but does not automatically load it.
>>
>> And interestingly setting the speed down to 400mhz on an Idle system does not 
>> change the measured power consumption, doing the same thing on an AMD powernow 
>> system (and I assume a actual Intel Speedstep) does lower the power used at 
>> idle.   Setting it down to 400 on a non-idle system does lower the power 
>> consumption as I would expect since it is now working slower.
>>
>> And notice that using that module does not change the bogomips on the system, 
>> were on an AMD powernow system it will change the bogomips.
>>
>>                                                  Roger
> 
> This is running on gentoo and an ancient P4B-M 
> 
> How are you measuring power?

External kill-a-watt power meter, plugged in between the wall and a UPS (I hate 
to reboot), doing the same test with AMD powernow under idle produces different 
results, idle with cpu at 1Ghz is lower power than idle with cpu at 2Ghz (I 
don't remember how much but I believe it was a significant amount (10+ watts at 
idle) ).

> 
> I also have the following turned on for idle savings:
> 
> CONFIG_CPU_IDLE=y
> CONFIG_CPU_IDLE_GOV_LADDER=y
> CONFIG_CPU_IDLE_GOV_MENU=y
> 
> Note that this is on a PXE system and all modules except nvidia are
> compiled in.
>

No pesky initrd for you I guess, that does make PXE booting easier.

 From doing a bit of reading it looks like p4_clockmod is not exactly like 
powernow and the speedstep.  Both powernow and speedstep actually change the 
clock frequency *and* lower the cpu voltage to get their powersavings, 
p4_clockmod only changes the clock speed (and may be appearing to change the 
clock speed through odd methods-and if it were just idling the cpu for periods 
of time that would explain the results) , and it looks like the default CPU_IDLE 
stuff is just as good as the clockmod stuff if the machine is actually idle, 
under load forcing the cpu down does lower the wattage used at a given point in 
time.

F8 has all but "CONFIG_CPU_IDLE_GOV_LADDER" set.

                            Roger